Merge two columns to combine counts and percentages

The cols_merge_n_pct() function is a specialized variant of the cols_merge() function. It operates by taking two columns that constitute both a count (col_n) and a fraction of the total population (col_pct) and merges them into a single column. What results is a column containing both counts and their associated percentages (e.g., 12 (23.2%)). The column specified in col_pct is dropped from the output table.

Usage

cols_merge_n_pct(data, col_n, col_pct, rows = everything(), autohide = TRUE)

Arguments

data

The gt table data object

obj:<gt_tbl> // required

This is the gt table object that is commonly created through use of the gt() function.

col_n

Column to target for counts

<column-targeting expression> // required

The column that contains values for the count component. While select helper functions such as starts_with() and ends_with() can be used for column targeting, it's recommended that a single column name be used. This is to ensure that exactly one column is provided here.

col_pct

Column to target for percentages

<column-targeting expression> // required

The column that contains values for the percentage component. While select helper functions such as starts_with() and ends_with() can be used for column targeting, it's recommended that a single column name be used. This is to ensure that exactly one column is provided here. This column should be formatted such that percentages are displayed (e.g., with fmt_percent()).

rows

Rows to target

<row-targeting expression> // default: everything()

In conjunction with columns, we can specify which of their rows should participate in the merging process. The default everything() results in all rows in columns being formatted. Alternatively, we can supply a vector of row IDs within c(), a vector of row indices, or a select helper function. Examples of select helper functions include starts_with(), ends_with(), contains(), matches(), one_of(), num_range(), and everything(). We can also use expressions to filter down to the rows we need (e.g., [colname_1] > 100 & [colname_2] < 50).

autohide

Automatic hiding of the col_pct column

scalar<logical> // default: TRUE

An option to automatically hide the column specified as col_pct. Any columns with their state changed to hidden will behave the same as before, they just won't be displayed in the finalized table.

Value

An object of class gt_tbl.

Comparison with other column-merging functions

This function could be somewhat replicated using cols_merge(), however, cols_merge_n_pct() employs the following specialized semantics for NA and zero-value handling:

1. NAs in col_n result in missing values for the merged column (e.g., NA + 10.2% = NA)

2. NAs in col_pct (but not col_n) result in base values only for the merged column (e.g., 13 + NA = 13)

3. NAs both col_n and col_pct result in missing values for the merged column (e.g., NA + NA = NA)

4. If a zero (0) value is in col_n then the formatted output will be "0" (i.e., no percentage will be shown)

Any resulting NA values in the col_n column following the merge operation can be easily formatted using the sub_missing() function. Separate calls of sub_missing() can be used for the col_n and col_pct columns for finer control of the replacement values. It is the responsibility of the user to ensure that values are correct in both the col_n and col_pct columns (this function neither generates nor recalculates values in either). Formatting of each column can be done independently in separate fmt_number() and fmt_percent() calls.

This function is part of a set of four column-merging functions. The other three are the general cols_merge() function and the specialized cols_merge_uncert() and cols_merge_range() functions. These functions operate similarly, where the non-target columns can be optionally hidden from the output table through the hide_columns or autohide options.

Examples

Using a summarized version of the pizzaplace dataset, let's create a gt table that displays the counts and percentages of the top 3 pizzas sold by pizza category in 2015. The cols_merge_n_pct() function is used to merge the n and frac columns (and the frac column is formatted using fmt_percent()).

pizzaplace |>
  dplyr::group_by(name, type, price) |>
  dplyr::summarize(
    n = dplyr::n(),
    frac = n/nrow(pizzaplace),
    .groups = "drop"
  ) |>
  dplyr::arrange(type, dplyr::desc(n)) |>
  dplyr::group_by(type) |>
  dplyr::slice_head(n = 3) |>
  gt(
    rowname_col = "name",
    groupname_col = "type"
  ) |>
  fmt_currency(price) |>
  fmt_percent(frac) |>
  cols_merge_n_pct(
    col_n = n,
    col_pct = frac
  ) |>
  cols_label(
    n = md("*N* (%)"),
    price = "Price"
  ) |>
  tab_style(
    style = cell_text(font = "monospace"),
    locations = cells_stub()
  ) |>
  tab_stubhead(md("Cat. and  \nPizza Code")) |>
  tab_header(title = "Top 3 Pizzas Sold by Category in 2015") |>
  tab_options(table.width = px(512))

Function ID

5-17

Function Introduced

v0.3.0 (May 12, 2021)

See also

Other column modification functions: cols_add(), cols_align(), cols_align_decimal(), cols_hide(), cols_label(), cols_label_with(), cols_merge(), cols_merge_range(), cols_merge_uncert(), cols_move(), cols_move_to_end(), cols_move_to_start(), cols_nanoplot(), cols_unhide(), cols_units(), cols_width()